Solar energy collection systems previously available or proposed for use have typically included a circulating fluid which is heated by energy concentrated in one of a variety of ways onto the fluid. The heated fluid is typically either used directly to exchange heat with a second lower temperature fluid for immediate use or is stored for subsequent use as needed. Storage of heat energy of solar or other origin is therefore seen to be known in the art, phase change heat storage systems particularly providing maximum storage of both latent and sensible heat. Such heat storage systems can have heat energy withdrawn therefrom as long as the temperature of the storage medium remains at a sufficiently high level relative to ambient. It is further known to use heat pump apparatus in both heating and cooling modes to extract heat from either the atmosphere or from air present in environmental spaces, the use of such heat pump apparatus typically requiring the expenditure of significant amounts of expensive energy.
In the present invention, solar energy is utilized to provide the primary source of power for a heating system, the system being supplemented by a heat pump driven by standard sources of energy, particularly for cooling purposes. A back-up heating system of conventional design can also be employed to assure adequate heating under all conditions. Since solar energy is used as the primary source of power with only a portion of the energy required to operate the system being relatively more expensive electrical or other energy, the present system is far less costly to operate than conventional gas, oil, or electrical systems presently in use. Further, the present system provides significant advantages over prior solar energy systems due to an efficient combination of solar energy collection, storage, and utilization with heat pump assistance, the utilization of a heat pump in the present system providing a flexibility and efficiency of operation not previously to be found in the art. In particular, solar-derived energy is utilized directly in the present system as an input into the evaporator of the heat pump, thereby allowing the utilization of substantially lower temperatures in the solar energy collection medium due to the potential embodied in the present system to transfer the heat energy present in the collection medium (even at lower temperatures than is possible with prior systems) to the evaporator of the heat pump. Since the present system is thus operable during sun conditions at which other solar systems are effectively inoperable, the system is capable of functioning directly from energy as it is collected. The ability to operate at lower collection medium temperatures results in lower heat conductivity losses, thereby rendering the solar energy collection sub-system of the invention more efficient. Stored heat energy will be depleted in the present system should the withdrawal of heat energy exceed heat input from the solar energy collector. When prior art "solar heat only" systems would be shut down due to the nonavailability of useable heat reserves, the present system is capable of switching to a "water to air heat pump" mode, thereby allowing the extraction and use of the normally unuseable stored heat. In such a situation, additional heat input from the solar collector could continue to be used.
The present system further provides an energy storage sub-system having phase change energy storage capability, the phase change storage capability being particularly useful during the heat cycle of the system unlike prior systems which embody phase change storage capability. Energy storage capability is further embodied in the present system in a water storage tank, latent and sensible energy being thereby stored in both a phase change storage tank and in a water storage tank, the phase change storage tank operating within a different phase change temperature range than does the water storage tank when utilizing heats of fusion. When storage capability is exhausted, the present system provides for direct expansion operation particularly for cooling in a manner not previously available in the art.
The present system can be operated on an annual basis without the need for calculation and effective maintenance of a seasonal "balance" of heat gain and loss, the system being therefore more flexible in operation than are the relatively passive "ice" storage systems presently under study. During the heating cycle of the present system, for example, versatility is clearly shown by the potential use of several optional modes of operation, particularly the "solar only" mode, "water-to-air heat pump" mode, and "air-to-air heat pump" mode, a supplemental heating system of conventional design being capable of incorporation into the system as a back-up. The present system further provides the ability to heat domestic water even during the cooling cycle of the system.
Accordingly, it is an object of the present invention to provide a heating and cooling system capable of providing comfort climate control of environmental living spaces and other indoor areas which utilizes solar energy as the primary energy source and which incorporates a heat pump into the total system for more efficient utilization of energy collected and stored in the system.
It is a further object of the present invention to provide a solar heating system having a heat pump incorporated thereinto for utilization of energy stored in phase change storage sub-systems utilizing materials which undergo phase changes involving substantial latent heats of fusion, the latent heat of fusion and sensible heat stored in the phase change materials being utilizable in the present system to a degree not previously attainable in the art.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.